Four muscles are shown below. Based on their fascicle arrangement, which muscle doesn't belong in the group?

• A. Rectus Abdominis.
• B. Interossei.
• C. Bicep Brachii.
• D. Sternocleidomastoid.

Answer: (B)

Verified step by step guidance

1. Identify the fascicle arrangement of each muscle: Rectus Abdominis has a parallel fascicle arrangement, Interossei have a pennate arrangement, Bicep Brachii has a fusiform arrangement, and Sternocleidomastoid has a parallel arrangement.
2. Understand the characteristics of each fascicle arrangement: Parallel muscles have fibers that run parallel to the length of the muscle, fusiform muscles are spindle-shaped with a central belly, and pennate muscles have short fibers that attach obliquely to a central tendon.
3. Compare the fascicle arrangements: Rectus Abdominis and Sternocleidomastoid both have parallel arrangements, while Bicep Brachii is fusiform, and Interossei are pennate.
4. Determine which muscle has a different fascicle arrangement: The Interossei muscles have a pennate arrangement, which is different from the parallel and fusiform arrangements of the other muscles.
5. Conclude that the Interossei muscle does not belong in the group based on its unique pennate fascicle arrangement compared to the others.